Hunger, appetite and satiation state. Substance and energy exchange, thermoregulation. Oral cavity role in these reactions.

Purposeful behaviour as for food taking is in the state which has received the name hunger state. This is special motivation directed on dyscomfort liquidation, connected with nutrients insufficiency in organism. Hunger center is located in hypothalamus, its excitement is delt both with nervous and humoral factors. Important role in sensations forming connected with hunger plays afferent impulsation coming in central nervous system from alimentary tract receptors. Its different parts have their own electrical basal rhythms of food taking. Near-houred rhythms are evacuational activity regulators. Intestine main activity rhythm – is of 90-minutes. There is 20-minute period of stomach and small intestine activity, liver, pancreas and intestinal glands secretory activity in this rhythm and 70-minute period of relative rest. Activity occurs in stomach and gradually passes through small intestine. Periodic activity initial reason is physiological hunger state. Empty stomach and small intestine proximal part hungry activity increases hunger state. It causes unconscious motor anxiety in animals and, conscious, in people. Inhibitory influencings of this feeling are connected with autonomic nervous system sympathetic part. Hypoglycaemia acting on specialized hypothalamic glucoreceptors participates in hunger forming.

Appetite – is emotional sensation delt with striving for food taking. This sensation may be hunger part but also it can occur independently from physiological consumption. In this case it is the expression of congenital or aquired individual predisposition to definite food type. One should underline that food taking in human being is not always connected with hunger feeling and it is rather uncorrect. But, unfortunately, it is so. Why? The answer is very simple – habit to take food in definite time (by the way, it is not the worst variant) or because all surrounding people are eating at this time.

Satiation - appears as a result of food taking. It occurs because of oral cavity, pharynx, oesophagus, stomach, duodenum mechanoreceptors as well as olfactory and gustatory receptors stimulation. Such satiation is called sensor or primary. We have also secondary or metabolic satiation connected with hydrolysis products coming into blood. It appears usually after 1,5-2,0 hours after primary satiation. Peptide hormones decreasing alimentary behaviour (cholecystokinine, somatostatine, bombesine, calcitonine) or increasing it (gastrine, insuline, oxytocine) are essential for food taking regulation, hunger and satiation sense occurence.

Remember! The slower you will take food (to masticate longer, not to hurry up while transition from one dish to other) the faster and at less food amount (it is the most important!) satiation will come. Commonly, food must be taken till you won’t feel that you can eat the same amount. Than you must leave the table. You are feeling hunger but after some time you will fell the satiation. This is one of elements of feeding culture!

Substance and energy exchange – is an integrity of physical, chemical and physiological processes of substances and energy transition in human organism as well as substance and energy exchange between organism and environment. Substance and energy exchange provides organism plastic and energetic needs. One can differentiate 2 interconnected but directed oppositely processes. Anabolism – is the integrity of organic substances, cellular components and other tissular and organic structures biosynthetic processes. They are growth, development, biological structures renewal and continuous macroergs resynthesis as well as energetic substrates accumulation. Catabolism – is the integrity of complicated molecules, cellular components, tissues and organs destructive processes to simple substance. Nutrients rich in energy are assimilated and chemically transformed but ending metabolism products with lower energy content are released from cell. Organism must receive energy in suitable form for it from environment and return into environment corresponding energy amount in a form suitable for further usage. This process in organism is called energy exchange. All processes generating energy that require molecular oxygen participation are formed aerobic exchange system. Energy generation without oxygen participation is called anaerobic exchange.

Definite part of energy accumulated in fats, proteins and carbohydrates chemical bonds is used in course of biological oxidation process for ATP synthesis, other part is transformed in warmth. This warmth, released right after in nutrients biological oxidation process has received the name primary warmth. Energy accumulated in ATP and used further for chemical, transport, electrical processes performance, mechanical work producing transformed in warmth was named as secondary warmth. If to measure all warmth quantity having been formed in organism for 24 hours then this warmth will be the measure of nutrients chemical bonds sum energy taking into account that these nutrients underwent biological oxidation in course of measurement. According to warmth quantity having been formed in organism one can make the conclusion about energy expenditures to viability processes performance. Main energy source in organism for viability processes performance is nutrients biological oxidation. Oxidation is essential for this oxidation. Thus, having measured consumpted oxygen quantity for 1 min (1 hours, 24 hours) one can say about organism energy expenditures size. There is a connection between oxygen quantity consumpted by organism for time unit and the quantity of warmth having formed in it for the same time. This connection is expressed through oxygen caloric equivalent – warmth quantity forming in organism at consumption 1 l of oxygen by it. For instance, it is equal to 5,05 kcal at carbohydrates burning.

Organism energy expenditures assessment may be performed by 2 ways:

· Direct biocalorymetry – is based on warmth quantity measurement directly disseminated by organism in warmth-isolated camera. It is a very exact method but it is used very seldom because it is cumbersome and expensive. This method principle is based on thermodynamics first law which means that all work transforms into warmth which we measure in calorymeters.

· Indirect biocalorymetry – is based on measurement oxygen quantity consumped by organism and further energy expenditures estimation with usage of data about respiratory coefficient (RC) and oxygen caloryc equivalent.

Respiratory coefficient – is released carbonic dioxide volume correlation to used oxygen volume. Given method essence can be described on the example of glucose oxidation: С₆Н₁₂О₆ + 6О₂ = 6СО₂+6Н₂О. This reaction is well known for you from biology, chemistry and biochemistry courses. Released carbonic dioxide volume is equal to one of used oxygen. Thus, at glucose oxidation RC= 6СО₂/О₂=1. In case of fats oxidation it is equal to 0,7, proteins – 0,8.

As all nutrients in organism are undergone to oxidation simultaneousely than after RC size determining one can approximately tell about dominant oxidation of one or other nutrient type. Every nutrient has its own energy valuation. That’s why on RC size one can estimate oxygen caloryc equivalent. If we know oxygen consumped amount we can estimate energy expenditure.

Organism energy metabolism consists of basal exchange and working addition.

Basal metabolism – is minimal level of expenditures necessary for organism viability support. It is defined under conditions of relatively complete physical and emotional rest. Under relative rest energy is expended to nervous system functions perfomance, constant substance synthesis, ion pumps work, body temperature support, respiratory musculature, smooth muscles, heart and kidney activity.

Basal metabolism determining is realized: in the morning, under rest state, on an empty stomach (the latest food taking must be 10-12 hours before investigation), at comfort temperature (22-24°C). Indicated standard conditions characterizes those factors which can influence on metabolism intensivity in human being. Metabolism intensivity is subjected to daily fluctuations. It is increased in the morning and is decreased in the night. It is changed at environment temperature changing (if it is below comfort zone than metabolism reactions intensivity is increased). In winter – is rised up, in summer – is reduced. Nutrients consumption, their further digestion (especially protheins) influence greatly on metabolism level. Metabolism intensivity and organism energetic expenditures increasing under food influence as for exchange and energy expenditures level taking place before eating is called specifically-dynamic food action. It is explained by energy expenditures to food digestion. Such food action may be up to 12-18 hours. It is mostly expressed at prothein food taking increasing metabolism intensivity up to 30 per cent and less significant at mixed food taking increasing metabolism intensivity up to 6-15 per cents. In babies specifically-dynamic food action is approximately on 30 per cents weaker than in adults. Prothein food causes basal metabolism increasing in children on 15-18% (in adults – on 30%); carbohydrate – on 10% (in adult – on 15%); fat – on 5% (in adult – on 15%).

In average basal metabolism size for person with mass 70 kg corresponds to 1600-1700 kcal /day (in women – less on 5-10%). Such factors as musculature development degree, liver, brain, heart, kidney, endocrine glands state influence on basal metabolism level. Basal metabolism is increased in small children with maximal velocity in the first year after birth (approximately from 120 to 600 kcal/day). After this basal metabolism growth is retarded again and accelerated again in puberty. But in children of any age basal metabolism level on 1 kg of mass is higher than in adults. It testifies to substance and energy metabolism more intensivity in children’s tissues comparatively to those in the adult. Basal metaboilsm in children depends on constitution. In thin and agile children basal metabolism is higher than in thick and dismoved. Basal metabolism is increased at fever (in average, on 5 per cent while body temperature increasing on 1°C).

Basal metabolism changes more than on 10 per cent may serves as diagnostic criterium of such organism states as thyroid dysfunctions, recovery after hard and durable diseases, intoxication and shock.

Basal energy metabolism plus working addition (something delt with working activity type) is equal to general (gross) metabolism. It is the characteristics of daily energy consumption. Its level depends on energy scale for different population groups.

Population groups and norm for them in kcal/day:

1-st – servant: men - 2500-2800, women – 2200-2400 (we belong to this group as people of

mental activity.

2-nd – workers of light physical activity: men – 2750-3000, women – 2350-2550.

3-rd – of middle on gravity physical activity: men – 2950-3200, women – 2500-2700.

4-th – workers of hard physical activity: men - 3450-3700, women - 2900-3150.

5-th – of very hard work: men - 3900-4300. Women mustn’t be in this group.

Some scientists add one group – of non-working pensionners – their energy expenditures after their work stoppage must be significantly shortened and be not higher than in people of the 1-st group.

Mental activity doesn’t require too significant expenditures like physical activity. Expenditures are rised up at mental activity in average only on 2-3 per cent. But mental activity accompanied by light muscular activity, psycho-emotional tension, leads to expenditures increasing on 11-19 per cent and even more.

Substance and energy metabolism regulation. It includes regulatory systems of multiple organism functions – respiration, blood circulation, excretion, thermoregulation and others. Hypothalamus plays role of substance and energy metabolism regulator. It is explained by the fact that there are nervous nuclei and centers there influencing directly on hunger and satiation and thermoregulation. Autonomic nervous system parasympathetic and sympathetic parts serve as metabolism regulation efferent system. Mediators releasing on their endings influence directly or indirectly through secondary messengers on tissues function and metabolism. Endocrine system is managed by hypothalamus and serves as substance and energy metabolism efferent system. Hypophysis, hypothalamus and other endocrine glands hormones influence directly on cells growth and development, supporting in blood necessary level of different substances (glucose, free fat acids, mineral ions and others). Cell is essential effector in these reactions. The most freaquent effects of regulatory influencings to cell are the following changes: of catalytic enzymes activity and their concentration, modulators, adenylates, common predecessors and common intermediate products action. Glucose concentration in blood (under norma it is equal to 0,8-1,2 g/l) is one of environmental integral indexes reflecting metabolism in organism. Eating act is both alimentary function powerful stimulator and gas exchange in organism. One can see both qualitative and quantitative metabolism changes. These changes character and level (size) depend on food chemical nature. Protein food taking is a sygnal to change primarily in protein metabolism and carbohydrate food consumption – in carbohydrate metabolism. Food ration qualitative and quantitative content may occur pathogenetic factor in some dental diseases development. Excessive feeding doesn’t influence directly on oral cavity organs state. But there occur metabolism diseases accompanied by teeth and mucosa injury under these states. Raw, solid food usage, its careful mastication encourages dental surface clearence and prevents dental covering forming. In people using porridge-like food dental covering is formed that may lead to caries and parodontosis development. Nutrients correlation disorder in food ration may be the reason of diseases taking place in oral cavity. For example, at excessive carbohydrates usage fermentation processes are enforced that favours microbes reproduction creating acid environment in oral cavity. Dental covering formation is increased on teeth, enamel dissolving is occured under these conditions that lead to cariesogenic teeth injury. That’s why carbohydrates predominance in food ration requires vitamine B₁ (thyamine) increased content. Food usage with excessive protein content creates alkaline environment in oral cavity that may be the reason of gums disease (gingivitis). On the contrary, protein insufficiency leads to hypovitaminosis of B group vitamines. Oral cavity and lips are very sensitive indicator of vitamine insufficiency in food ration. It is explained by their rich blood supply and capillary net. Capillaries endotheliocytes respond subtly to vitamines content in blood. Vitamines play important role in oral cavity protection and its regeneration. Mucosa with less resistance is easier injured and harder regenerate than intact tissue of organism well-supplied by vitamines. Bacterias located in oral cavity cause inflammation easily at mucosa increased resistancy. Pathologic symptoms are always originated from the place where mucosa is undergone to mechanic action (mastication).

Avitaminosis may be developed at vitamines consumption decreasing, their usage disorder, increased need in them. Vitamine “A” deficiency causes oral mucosa epithelium keratinification, small submucose salivary glands atrophy (the latest fact lead to hyposalivation). Mucosa becomes dry, many cracks occur on it which are inficated easy that results into inflammational processes. Insufficiency of “B” vitamine group is expressed usually by oral mucosa inflammation, atrophyc locuses existance on one’s tongue, its swelling, angular cracks. Large vitamine “C” deficiency in the adult causes zinga. Zinga is characterized by spontaneous bleedings particularly from gums. Gums are swelled, red-zyanotic. As a rule, secondary infection is connected that enforces the bleeding. Teeth are covered with inficated and that’s why stinking blood clot. Grey coating covers gums margin, painful ulcers are formed. At big inflammation duration gums and interdental papillas necrosis occurs. Vitamine “D” deficiency in odontogenesis disturbs enamelogenesis.

Among many factors determining diet quantitative properity chemical elements (micro- and macroelements) play important role. The biggest amount of elements from Mendeleev’s table were found in uninjured tooth. Changes in dental-maxillar system may be linked with insufficient food mineralization (calcium, phosphorus), insufficiency or excessiveness of microelements content (iod, fluorum). While coming in organism through alimentary tract, they influence actively on various physiologic processes particularly on bones and teeth mineralization. Resistancy or predisposition to caries, mineralization and demineralization processes in course of odontogensis and in formed tooth under norma and at pathology depend on microelements together with many other factors.

Essential condition of alive organism existance is thermal exchange between organism and external environment.

Thermal exchange and body temperature regulation. Temperature influences greatly on alive processes course in organism. Physico-chemical base of this influence is chemical reactions course velocity change. That’s why body temperature influences upon its cells activity. Organism tissues temperature is defined by cellular structures metabolic thermal production velocity correlation to forming warmth dissemination velocity into environment. Such processes velocity correlation disorder leads to body temperature change. Mechanisms fixed in course of evolution by means of which organism may express resistance to lower and higher environmental temperature are essential for this.

All organisms according to mechanisms of homeostasis supporting are divided into 3 main groups:

· poikylothermal – changeable, which have no the ability to support body temperature on constant level, cold-blooded – amphibias, reptiles, fishes, crustaceas;

· homoiothermal – similar, warm-blooded, which can support body temperature on relatively constant level with daily and season fluctuations in the limits of 2 degrees – mammals, human beings;

· poikylohomoiothermal – under favourable conditions they belong to homoiothermal organisms, under unfavourable – to poikylothermal. Some insects reproduced by partenogenesis (ants, thermites, beans), colibry, crocodiles, tortoises, rodents, Chiroptera (flying mice) belong to this group.

Body temperature constant level in humans may be served only under the condition of dynamic equllibrium between heat production and heat emission. Such equillibrium is supported by thermoregulation physiologic mechanisms. One can differentiate 2 ways of thermoregulation: chemical and physical.

I. Chemical thermoregulation is performed by means of enforcement or weakening of cellular and tissular metabolism intensivity and expressed in heat production amount change. Heat source in organism are many organs and tissues but portion of their participation in heat production is rather various. Maximal heat production in organism occurs in muscles, liver and kidneys. One can say about 2 thermogenesis types:

1) Contractive – is linked with muscular thermoregulative activity. In turn, one can differentiate 2 subtypes of it:

· Thermoregulative tone - is analogous to muscular pose tone. It is performed like low-freaquened incomplete tetanus (impulses freaquency is 16 per 1 minute). Muscles of neck, trunk and extremities flexors are involved in this reaction. That’s why human being changes his pose (curls up into ball).

· Trembling – in switched on when internal body temperature becomes its reducing.

2) Non-contractive – connected with activation of heat special sources is realized due to brown fat tissue existance which in comparison with white fat has more mitochondrias (brown colour is provided by iron-containing enzymes – cytochromes which are important part of mitochondrial oxidative enzymatic system. Fat acids oxidation velocity in it predominates that in white fat in 20 times.

II. Physical thermoregulation is realized by means of heat emission changes. One can differentiate several heat emission ways:

· Heat radiation – heat releasing (emission) by organism due to infrared radiation out off body surface. Under rest state heat emission by this mechanism is about 60 per cent.

· Heat conduction and convection – direct heat emission to subjects attached to skin, air. It is the more intensive the more is temperature difference of body surface, air, surrounding subjects. Organism losses up to 15 per cent of warmth by this method.

· Evaporation – the way of heat dissemination by organism into surrounding environment due to its expenditure to sweat or moisture perspiration from skin surface and moisture from mucosae. Organism looses up to 19-20 per cent of heat by evaporation.

Thermoregulation is body temperature constant level supporting. It is performed by principle of self-regulation. Receptor structures - are receptors of coldness, warmth and burning. They are located in skin and mucosae. Excitement threshold for receptors of coldness (their amount is bigger and they are located more superficial than receptors of warmth) is in limits of 20-33°C (average - 26°C); for receptors of warmth - 40-46°C (average - 43°C) and for receptors of burning – everything that higher than 45°C.

Thermoregulative center is located in hypothalamic nuclei. Physical thermoregulation is performed by hypothalamic nuclear group located between anterior comissure and optic chiasma (heat emission center). Shortly, heat emission center is located in posterior hypothalamus. Under comfort (thermoneutral) conditions thermal equillibrium providing body temperature support at normal level is not in need of correction by special thermoregulative mechanisms. Environment temperature below than comfort causes activity increasing in perypheral receptors of coldness. This “cold” information increases the posterior hypothalamus efferent structures tone and causes hypersympathycotony as the result of such increasing. It is accompanied by cutaneous and subcutaneous vessels tone increasing. Result of these reactions: organism isolation increasing and heat serving by means of heat emission reducing. This process also leads to pilomotor reflex occurence (activation of smooth muscles fibres function rising hair covering). In parallel to this due to posterior hypothalamus work activating pose muscular tone regulatory system (thermoregulative tone and trembling appearence) heat production increasing occurs in organism (contractive thermogenesis). Due to adrenaline and noradrenaline releasing in course of this reaction energetic exchange in all tissues becomes stimulated particularly in brown fat tissue (non-contractive thermogenesis). Such heat production adrenergetic stimulation is triggered by thyroid hormones action the releasing of which is increased at cooling. When organism is warmed up coldness receptors activity is reduced that leads to hypothalamic efferent structures tone decreasing. As a result sympathetic nervous system influencies on cutaneous and subcutaneous vessels are reduced and this reaction is accompanied by cutaneous blood supply increasing. Heat exchange adrenergic and thyroid activation is decreased in parallel to this. Thermoregulatory center influencings decreasing causes muscular tone and thermogenesis reducing connected with it. Under over heating conditions special sympathetic structures are activated managing perspiration through cholinergic nervous fibres. Heat emission through evaporating is increased as a result of this.

Human body temperature under norma is about 37°C. It is changeable in course of 24 hours: maximal - to 16-18 hours, minimal – to 4 hours. If temperature is decreased - it’s hypothermia, if it is increased – hyperthermia. At temperature reducing below 35°C behaviour disorders take place, up to 31°C - human being is unconscious, at 24-26°C - he is dead. At body temperature increasing up to 39-41°C delirium can begin; at 41-43°C – heat shock and above 43°C - death. Sweat glands activity is essential for heat regulation. Their general amount on human body is up to 2,5 mln. The biggest number – on face, palms, soles, axillas (arm-pits). One can see constant (invisible) evaporation during which sweat is released from skin surface right after its emission. When forming sweat amount is big, it is accumulated near skin surface in drops (visible evaporation). Sweat releasing is observed not only in course of physical activity but also during mental activity. In course of psychical excitement and some emotions (fear, wrath, pain) cold sweat appears in people. Coldness sensation occurs because of skin cooling as vessels are constricted and skin blood supply is decreased simultaneousely with sweat emission. Sympathetic nervous endings in sweat glands are considered to be cholinergic i.e. containing mediator acetylcholine releasing while excitement. Impulses causing sweat emission at temperature increasing come into sweat glands through cholinergic nervous endings while causing emotional sweating (sweat releasing) – through adrenergic. Under norma sweat amount per day reaches up to 500-900 ml, in summer – in 2-3 times more. At high temperature and hard physical activity – in 5-10 times and even more significant.

Oral mucosa temperature is determined by sequence of factors:

· environmental temperature and humidity,

· cellular metabolism intensivity;

· tissues anatomo-physiological features;

· their vascular net state.

The latest factor depends on capillaries quantity and degree of their filling as well as on velocity movements in arterioles. Mentioned data explains oral cavity organs temperature indexes different topography. Oral mucosa temperature depends also on saliva evaporation from mucosa surface for example at oral breathing. It is also one of heat releasing way providing organism temperature constant level support. Besides, saliva and oral mucosa action that makes food temperature cooler or warmer (depending on necessity) is involved in thermoregulative functional system. It was established that every locus of mucosa has definite temperature. Inferior lip skin average temperature is equal to 33,1°C, superior lip - 33,9°C. Temperature is reduced in boarder region between skin and red lip limb (margin). Oral mucosa temperature is increased in caudal direction. Hard palate temperature is higher in its dystal parts and far from middle line.

Tooth temperature is also fluctuated in its different locuses with definite regularity: temperature is lower (30,4-30,5°C) on cutting limb and masticatory surface than in near-cervical region (30,9°C). They determine tendency to gradual temperature increasing in all crown’s regions towards from central incisives to molars.

Oral mucosa and maxillar-facial skin initial temperature should be taken into account at treatment application by warmth or coldness. At facial nerve injury in corresponding innervation zones on face temperature is decreased on 8-10°C. Usual thermal procedures application in these cases can cause temperature dyscomfort sensation and even pain. Tooth thermometry plays very important role in rational tooth preparation ways development in such regime at which enamel, dentine and pulp thermal trauma will be minimal. Dentist should remember that in course of caries cavity forming or tooth preparation under crown dental tissues temperature increasing occurs due to resistance (friction) of acting (cutting or grinding) instrument. Tooth temperature rising up higher than 45°C may be enamel and dentin burn reason and lead to pulp thermal trauma. For these phenomena prevention one should select instruments taking into account bors and preparational discs size and shape, their rotation velocity as well as material they are manufactured. Besides, one should follow working regime with all instructions perfomance. Essential condition is also preparation continuosity and usage methods possessing high velocity. Special attention is paid to cooling type, cooling system properity and correct flow direction to contact place of cutting instrument with solid dental tissues.

Oral mucosa may undergo to temperature influencies which differ significantly from body temperature in course of food taking. Cold dishes or drinking cause mucosa injury seldom because their used amount is usually little and they are located in oral cavity for short. Cooling influence on mucosa circulation by following way: vasoconstriction occurs first, then at firther cooling it is enforced and microcirculation is almost completely stopped.

Strong cooling, for example, by chlorethyl doesn’t destroy tissues and after its action stoppage their function are restored. Under heat influence hyperaemia is developed in mucosa and then after it - surrounding tissues oedema (swellimg). Hot dishes, warmed dental instruments (in course of activity) may cause mucosa restricted necrosis. Vesicle occurs despite burn which is ruptured soon with erosion forming. Thermal actions from oral receptors change circulation in salivary glands by reflectory way, that leads to saliva secretion increasing with different mucus, water, lyzozyme and other enzymes content.

 

 

Lecture 9